Plunger operated magnetic electric switch



March 1965 w. w. CRISSINGER ETAL 3,175,060

PLUNGER OPERATED MAGNETIC ELECTRIC SWITCH Filed Aug. 22, 1961 21 62 lllfli lllll llli y a 59 5U l INVENTORS.

United States Patent Office 3,175,060 Patented Mar. 23, 1965 The present invention relates to push key or push button structure, and more particularly to a snap-action push key construction.

In momentary contact electrical switches, particularly those in which a plurality of circuits are opened and closed by operation of the switch, it is important that the push button or key be moved through its full designed travel distance, so as positively to assure the opening and closing of the desired circuits and therefore the desired operation of equipment controlled by the switch. Otherwise, the controlled equipment will not operate, or operate improperly. Such momentary contact push-button operated switches may be employed, for example, in key-set telephones, as well as in various types of key-operated oflice and other equipment, such as typing or printing machines, calculating machines, and tabul-ating equipment, or the like. The problem is not limited to electrically operated equipment, since various devices operated through mechanical linkage by a push button or like key arrangement may require that the push button or key be moved through its full throw to assure the desired operation of the device.

The use of a spring, weight, or the like as biasing means to hold the push button or key in normal position, and requiring considerable force to move the key from the normal position, defeats itself because the farther the key is moved toward the operating position, the greater becomes the resistance of the spring or other biasing means, and the less likelihood there is of the full travel or throw of the key being eifected. The present invention provides a simple, inexpensive, and effective arrangement for assuring the full travel of the push button or key so as positively to obtain the desired operation of the controlled equipment. Essentially, the present concept involves the employment of magnetic means to hold the key in normal position, requiring considerable pressure on the key in order to overcome the magnetic attraction and effect movement of the push button or key, the resulting momentum and progressively decreasing magnetic attraction assuring movement of the key through its full travel distance or throw. In other words, the magnetic holding arrangement produces a snap action. Bi-asing means, which may be the mechanism or device upon which the push button or key operates, may be provided to assure return of the key to normal position.

It is an important object of the invention to provide a push button construction by which full travel between a normal position and an operating position is positively assured.

Another object is the provision of a push button switch construction in which the force required to overcome mag netic attraction holding the push button in normal position assures full travel of the push button to the operating position.

Another object is the provision of a push button construction for operating a mechanism by push-button movement between a normal position and an operating position, in which the momentum resulting from application of sutiicient pressure to overcome magnetic attraction holding the push button in the normal position assures full travel of the push button from normal to operating position.

Other and further objects, advantages, and features of the invention will be apparent to those skilled in the art from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a plan view of a key set employing a number of push buttons or keys according to the invention;

FIGURE 2 is a sectional view on an enlarged scale illustrating one of the push buttons and electrical contact means operated thereby, taken substantially as indicated by the line 2-2 in FIGURE 1;

FIGURE 3 is a View similar to FIGURE 2, but showing another embodiment of the invention;

FIGURE 4 is a view similar to FIGURES 2 and 3, but showing another embodiment of the invention;

FIGURE 5 is a similar View of another form of the invention;

FIGURE 6 is a plan view of one form of a permanent magnet which may be employed in the push button structures; and

FIGURE 7 is a plan view of a permanent magnet similar to that of FIGURE 6, but with a different arrangement of the north and south poles.

Referring first to FIGURES l and 2 of the drawings, there is shown a key set generally designated 10 comprising a number of push buttons or keys generally designated 11, twelve such push buttons being shown, mounted for longitudinal reciprocation in a supporting structure which may take any appropriate form. In the present instance, this structure is defined by a base plate 12 of non-magnetic material having formed therein twelve apertures 13 arranged in correspondence to the location of the push buttons 11, each of the apertures accommodating projection of the push button through the plate 12. On what, in the horizontal position of the plate 12 illustrated in the drawings, is the upper face of the base plate, there is disposed a panel 14, preferably of magnetic material, which is provided with apertures 15 respectively aligned with the apertures 13 to accommodate the associated push button 11. Mounted in spaced parallel relation to the panel 14 is a plate 16 of magnetic material apertured as at 17 in alignment with apertures 13 and 15. The mounting of plate 16 is in the present instance effected by means of studs 18, only one of which is shown, of non-magnetic material brazed or otherwise secured to the plate 16 and having their free end portions reduced and projecting through the plate 12 and panel 14. The reduced stud portions have the ends thereof threaded to engage with internally threaded space-rs 20, one of which is shown in FIGURE 2, for holding the plate 12, panel 14, and plate 16 in the assembled relation shown and described. Secured on the upper plate 16 is a hollow cover structure comprising a non-magnetic mounting panel 21 provided with apertures 22 and a dished cover 23 secured to the panel by any suitable means. The mounting panel is, in turn, bolted or otherwise fastened on the upper plate 16. The cover 23 has a central fiat portion in which are formed apertures 24 through which the head ends of the push buttons 11 extend. The mounting and panel cover apertures 22 and 24 are aligned with the apertures 13, 15, and 17, so that the push buttons may be ,reciprocated in the respective aligned openings, which serve to guide the push buttons, the several openings 15, 17, and 24 generally corresponding in size and shape to the push button portions accommodated therein. The apertures 17 of the plate 16 are larger than the openings 2 2 of the mounting panel so as to define recesses in the combined thickness of the plate 16 and panel 21, as will be clear from FIGURE 2, for a purpose explained hereinafter. Of course, the recesses may be otherwise formed.

The push buttons 11 comprise each a head portion 25 having a stem 26 extending therefrom. Each head may carry an identifying character or other indicia, as indicated in dotted lines in FIG. 1. The head may be integral with the stem, or may, for example, be made of plastic and secured on a stem of metal. On each stem 26 is secured, as by a suitable adhesive, a hollow sleeve 27 defining therewith a plunger portion. The

sleeve has a closed or solid end portion 28 formed with diametrically opposed flats 29, stop shoulders 30 substantially normal to the axis of the push button being defined by the flats between the tubular and solid portions of the sleeve. The sleeve 27 is formed of non-magnetic material and may advantageously be formed of a suitable plastic, such as nylon or the like. It will be obvious that the head portion 25 and the plunger portion of the push button may be formed in one piece, if desired, of any suitable material. Secured on each push button plunger portion is an annular permanent magnet 32, the plunger portion being disposed through the central aperture of the magnet. To facilitate assembly, the magnet is removably mounted by means of retainer rings 33 which engage in suitable grooves 34 formed circumferentially of the sleeve 27. The grooves are so located on the sleeve as to position the retainer rings 33 in closely'overlying relation with opposite faces of the magnet, and to dispose the magnet at the desired point longitudinally of the plunger portion of the push button or key 11. The rings 33 are made of a plastic, such as nylon, of sufiicient elasticityto allow'of their being drawn over the sleeve 27 and then to have their inner annular edge portions engage in the grooves. In the present instance, the groove 34 near the head 25 of the key 11 is formed of substantially double the width of the groove more remote from the head, to accommodate two retainer rings 33, while only a single ring is employed in the other groove. This affords greater strength in the magnet mounting at the point Where force 7 is elfectively applied to overcome the magnetic attraction by which the push button is held in normal position, as hereinafter more fully explained.

As will be clear from FIGURE 2, each key or push button 11 is disposed in one aligned group or series of openings 13, 15, 17, 22 and 24 of the respective plates and panels, with the magnet between panel 14 and plate 16. In the normal position of the push button, illustrated in FIGURE 2, the double rings 33 are engaged in the recess defined by the opening 22, the magnet 32 engaging against the plate 16 by reason of magnetic attraction and the accommodation of the rings in the recess, and thereby disposing the push button or key in normal position. The several panels and plates with the openings therein, and the corresponding shapes of the apertures and the portions of the key respectively disposed therein, provide a guide structure for the push button or key, to maintain it in desired relation for longitudinal movement in either direction. The stop shoulders 30 are so positioned as to allow the desired maximum movement of the push button from the normal to the operating position, in the direction from the plate 16 toward the panel 14, but engaging with the panel 14 to limit movement of the push button in such direction.

The push button is shown in FIGURE '2 as employed to control an electrical switch contact assembly, stack, or pile-up, generally designated 35, comprising a plurality of resilient contact arms 36 and a pair of. longer resilient lever arms 37, provided with contact points 38 at the free ends thereof. 'The arms and 37 are fastened together at the other ends thereof, separated from each other by insulating blocks 39, clampingly assembled on a base plate 40 by means of screws 41 or the like, the base plate being bolted or otherwise secured on the lower face of the base plate 12. An insulating strip 42 overlies the resilient arm 36 nearest the base plate at} to prevent electrical conduction therebetween. The stack or pile-up 35 thus extends below the plate 12, and

Cal

21. is arranged to have the resilient contact-carrying arms disposed with their free ends adjacent the aperture 13, the lever arms 37 projecting into the path of the solid end 28 of the plunger. The other ends of the resilient arms 36 and 37 are adapted for suitable connection to P threaded portions of screws 46 extending through the a 'plate 45.,

It will be apparent from FIGURE 2 that upon application of pressure to the head 25 of the push button '11 sufiicient to overcome the resistance of the magnet 32 to separation from the plate 16, the push button or key will be moved longitudinally so that the solid end portion 28 of the push button engages the upper lever arm 37 of the pile-up 35 and moves the resilient arms 36 and 37 so as to open and close the circuits in a predetermined manner through separation and engagement of the several contacts 38. The tip or end of the plunger portion is of electrically insulating material, which may be the non-magnetic material of the sleeve 27 or another material formed into suitable shape and secured to the sleeve. By reason of the block 43, the lower lever arm 37 is moved at the same time as the upper lever arm 37, as will be obvious. The resilience of the arms i 36 and 37 of the pile-up allows for considerable travel of the push button after engagement with the upper lever arm 37, so as to assure more than suificient movement of the plunger and arms for effecting the desired opening and closing of the several contacts 33. The actual travel of the key is determined by the spacing of the shoulders 30 from the panel 14, which engage the panel to stop the operating movement of the plunger. Return movement of the plunger is of course limited by engagement of the magnet 32 against plate 16, this representing the normal or non-operating position of the push button. As evident from the drawing, the operating movement of the push button is'greater than required to effect the desired opening and closing movement of the contactcarrying arms.

The separation ;of the magnet .32 from the plate 16 under pressure applied to the head 25 of the key is, as will be appreciated, rather sudden and abrupt. The result is that before the operator can react, the push button moves through its full travel to theoperating position determined by engagement of the shoulders 3% with the panel 14. Only the force of the resilient arms of the switch stack 35 presents any appreciable resistance to this movement, since the magnetic attraction decreases progressively as the magnet moves away from the plate 16. The force of the contact arms, even upon maximum deflection by the push button, is considerably less than the magnetic force holding the key in normal position. The arrangement thus results in a snap action of the push button resulting in full travel of the push button to assure the desired operation, the force employed to overcome the magnetic attraction acting substantially unchecked to drive the plunger to the operating position against the yielding opposition of theswitch mechanism contact arms. Upon release of the push button 11, the arms% and 37 not only return to their original or normal position by reason of their resilience, but by engagement of the upper lever arm 37 with the tip end of the plunger portion of the key also urge the key toward its normal position. As will be evident from the fact that a slight space is provided between the tip of the plunger portion of the key and the upper lever arm 37 in normal position of the parts, it is not necessary that the push button be returned completely to its normal position by the resilience of the arm 37, since the attraction between the magnet 32 and the plate 16 is more than suilicient to assure completion of the return movement of the push button. In fact, it is possible to provide a push button and magnet arrangement by which return of the push button is efifected by the magnetic attraction alone, if desired. ()rdinarily, it is preferable and less expensive to employ means for biasing the push button to its normal position from the operating position.

In the present case, the switch stack or pile-up 35, which is the mechanism or apparatus controlled or actuated by the push button, is employed as the biasing means for returning the push button to normal position, because the resilience of certain of its elements may be utilized for this purpose. It will, of course, be understood that the biasing may be achieved by separate or additional spring means, or in any other suitable manner.

In FIGURE 3, there is shown an embodiment of the invention which, while generally similar to that of FIG- URE 2, is specifically different. The support structure for the push buttons or keys 11 is generally like that of FIGURE 2. In this embodiment of the invention, however, a permanent magnet is employed as a fixed part of the support structure, and arranged to attract bodies of magnetic material mounted on the plunger portions of the push buttons, and the construction is therefore different in certain respects. A permanent magnet 50 is shown as disposed between a plate 51 of magnetic material which takes the place of the base plate 12 and bottom panel 14 of the construction shown in FIGURE 1, and a second plate 52 also of magnetic material, which takes the place of the upper plate 16 of the structure of FIG- URE 2. The magnetic plates 51 and 52 serve as pole pieces for the magnet 50, being of opposite polarity and arranged substantially parallel to each other by means of non-magnetic stubs 53 similar to the studs 18. While only one magnet 50 is shown in FIGURE 3, it will be understood that any appropriate number may be employed, depending upon such factors as the size of the pole plates 51 and 52, the distances between the push buttons 11 and the magnets, the strength of the magnets, and the like. The magnets may be secured between the plates 51 and 52 in good contact therewith, and with the poles in corresponding relation, by any suitable means. In FIGURE 3, the magnet 50 is shown as clampingly secured between the plates 51 and 52 by the spacers 53,

but it might be adhesively or otherwise secured. Projections 54 are struck from or otherwise provided on the plates 51 and 52 to engage the sides of the magnet for holding it in the desired location. The pole pieces or plates 51 and 52, it will be evident, serve as polar extensions of the magnet. If desired, such polar extensions may be formed as integral parts of the magnet.

The plate 51 has a plurality of apertures 55 therein, similar to the apertures 15 previously described, and in the pole plate 52 are formed a number of apertures 56 respectively aligned with the apertures 55 to receive the plunger portions of the keys reciprocably therethrough. A cover structure substantially identical to that of FIG- URE 2 is provided, comprising the non-magnetic mounting plate 21 secured on plate 52 and having attached thereto the dished cover 23, the plate and cover having the respective apertures 22 and 24 for the keys II. The keys in this embodiment, while of substantially the same form as in the embodiment of FIG. 2, have the plunger por tions made of magnetic material. Each key has a plunger portion 57 including a preferably integral stem portion corresponding to the stem portion as, on which is provided the head 25. The tip 58 of the plunger is formed of or covered by non-magnetic material, which is also electrically insulating if the push button is employed to operate the switch stack 35 or other electrical mechanism. Flats 29 and shoulders 39 are formed on the plunger 57 substantially as in the form of FIG. 2.

Secured on each push button 11 in any suitable manner is a disk 59 of magnetic material which is attracted toward the upper pole plate 52 to hold the push button or key It in its normal position. The disk may, for example, be threadedly mounted on the plunger or cemented by suitable adhesive, or as shown, secured by metal retainer rings 60 overlying the opposite disk faces and engaged in grooves in the plunger 57. It is to be noted that in this case the support structure does not provide a recess for the retainer ring 66 which overlies the upper face of the disk 59. About the plunger 57 is disposed an annular pad 61 of nylon, plastic or other suitable material, which in the normal position of the push button is engaged between the pole plate 52 and the ring 60, serving to eliminate clicking or other noise, and to reduce jarring in return of the push button to normal position. The pad 61 may be cemented or otherwise secured to the plunger, retainer ring, or plate 52, or may be loosely disposed between the plate and disk. Furthermore, the thickness of member 61 between disk 59 and plate 52 is predetermined to control the desired degree of normal magnetic holding force. In this construction, a spring 62 is provided between the disk 59 and pole plate 51 biasing the disk toward the pole plate 52, or in other words, biasing the push button or key 11 toward normal position. It is to be understood that the spring 62 may be employed in place of or in addition to biasing means such as the switch stack or pile-up 35, or other mechanism or apparatus operated or actuated by the push button which applies a biasing force to the push button urging it toward normal position. Thus, for example, the push button 11 might operate to act upon a linkage or lever system moved to a given position by depression of the push button, and in such position applying a force, due to gravity or other causes, tending to return the push button to its normal position. As with the construction of FIGURE 2, of course, biasing means aside from the magnet itself might be dispensed with.

The plunger 57, by reason of its magnetic permeability, provides a flux path between the pole plates 51 and 52 at all times, to complete a magnetic circuit from magnet 50 through one pole plate, the plunger, and the other pole plate back to the magnet, this flux path not urging the plunger to move axially.

The disk 59 in moving to normal position augments this path providing a lower reluctance working path for the magnetic flux.

It should be understood that in order to prevent drag due to magnetic material rubbing over magnetic material, the portions of plunger 57 adjacent to magnetic plates 51 and 52 might be plated with non-magnetic material such as chrome; or plate 21 might be of nylon with the aperture thereof surrounding plunger 57 of smaller dimension than the aperture in plate 52 and a similar auxilary plate of nylon might be used in conjunction with plate 51.

In FIGURE 4, there is shown still another embodiment, generally similar to that of FIGURE 3 but differing therefrom in certain respects. In the structure of FIGURE 4, the support of each push button or key 11 is substantially the same as in the structure of FIGURE 3, pole plates 51 and 52 being provided with one or more magnets 50 secured therebetween as in the construction of FIGURE 3, the non-magnetic studs 53 being employed to secure the plates in the spaced parallel relation disclosed with the magnet clamped therebetween. The cover structure comprising the mounting plate 21 and cover 23 is provided and mounted on the upper pole plate 52 in any appropriate manner. In this form of the invention, the base plate 12 of non-magnetic material is disclosed as employed, underlying the pole plate 51. The base plate 12, of course, might be omitted as in the structure of FIGURE 3, or might be employed in the FIGURE 3 embodiment, if desired. Apertures 13, as previously de- 7 scribed, are provided in the plate 12, in alignment with the apertures 55 and 56 of the pole plates Sit and 52, and with the apertures 22 of plate 21 and the openings 24 in the flat central position of the cover 23. The keys 11 are similar to the keys or push buttons of the embodiment of FIGURE 3, each having the plunger portion 57 of magnetically permeable material with the non-magnetic, and optionally insulational tip 58. The flats 29 and shoulders 30 are provided as previously described, although the latter are not necessary. As in the construction of FIGURE 3, the plunger 57 and disk 7 ii provide a flux path between the plates 51 and 52 to complete a magnetic circuit.

Secured on the plunger 57 like the disk 59', but in this case threadedly, is a disk 70 formed of suitable magnetic material so as to be attracted by the pole plate 52 of magnet or magnets 50 to hold the push button or key 11 in the normal position shown. The push button is biased toward the normal position by a spring 71 which surrounds the'disk and bears at one end against the pole plate 51 and at the other against a snap ring 72 engaged in a suitable circumferential groove 73 formed in the disk 70. Other laterally outwardly projected means might be used instead of the split ring 72 for engagement by the spring 71, as will be obvious. It will be evident that, if desired, the spring 71 might be engaged with the disk 70 in any other appropriate manner, such, for example, as the engagement between the spring 62 and disk 59 in FIGURE 3, and that, if desired, the spring 71 might be replaced or supplemented by other biasing arrangements, as already disclosed. The disk 7% is of suflicient thickness or axial dimension to extend, in normal position of the push button, substantially from the plate 52 to the plane of the shoulders 30. Annular sound-deadening pads 61 are disposed in any suitable manner betwen the faces of the disk and the adjacent pole plates 51 and 52, being mounted in any suitable manner, as in the case of the pad 61 in the structure of FIGURE 3. As in that structure, the plate 52 is not recessed, so that the disk 70 engages against the plate, except for the interposition of pad 61, in the normal push button position. Upon operation of the push button 11, not only does the attraction between the plate 52 and the disk diminish as the plunger moves toward operating position, but the attraction of the pole plate 51 for the disk increases progressively,counteracting in part the force of the. spring 71 or other biasing means.

The snap action of the key in moving from normal to operating position is thus augmented by the arrangement utilizing the magnet structure to draw the plunger toward operating position. Although the attraction between the pole plate 51 and disk 70 must be weaker than the force of the return spring '71 or other biasing means if the latter is to be effective in urging the key to normal position,

it does provide a partial counterbalance to the biasing means, and thus makes it more certain that the plunger will move through its full designed travel distance, and therefore that the desired operation will be effected. It

, will'be' apparent that the progressive increase in the magnetic attraction between the disk '76 and pole plate 51 as the plunger moves toward operating position is particularly advantageous because it occurs concurrently with progressive increase in the biasing force of the spring 71 as it is compressed by the same movement of the plunger, thus providing a force opposing and generally paralleling in value the force of the spring urging the plunger to normal position. In this construction, also, the disk 76 engages with the plate 51 upon movement of the key to operating position, save that the sound-deadening pad 61 is interposed, and the disk thus may be employed as a stop limiting operating movement of the push button, either alone or in cooperation with the shoulders 30. It is for this reason that the shoulders are not necessary.

7 Accordingly, the flats 2% may be omitted to eliminate the shoulders, if the prevention of rotation resulting from provision of the flats is not required or is otherwise achieved.

It may be noted that the structures of FIGURES 3 and 4 provide a buffer arrangement cushioning the movements of the push button to eliminate or minimize noise, thus effecting quiet operation. These structures also provide a path for magnetic flux between the pole plates 51 and 52 of the magnet structure or arrangement, this path being through the magnetically permeable plunger 57, which thus acts as a keeper bridging the poles of the magnet.

The construction illustrated in FIGURE 5 is generally similar to that of FIGURE 2, employing the base plate 12, bottom panel 14, upper plate 16, and mounting plate 21 secured on plate 16 and carrying the cover 23. The upper plate 16 is mounted in spaced parallel relation to the base plate 12 and panel 14 by means of the nonmagnetic studs 18 as previously described, with which the spacers 20 may be employed. The keys 11 each employ substantially the identical construction disclosed in connection with the embodiment of FIGURE 2. An annular magnet 80 generally similar to the magnet 32 previously described is secured to the lower face of the plate 16, with its central aperture in alignment with the aperture 17 of the plate accommodating the sleeve 27 of the push button 11. The disk may be secured as by a layer of suitable adhesive 81, or other appropriate means. The plate in, it will be understood, in this case need not be of magnetic material. An annular disk 82 of magnetic material is mounted on the sleeve 27 of the push button by means of the rings 33 as heretofore explained, so as V to be attracted by the magnet 3% to hold the push button in the normal position. In the present instance, the disk 82 is shown as arranged to have full face contact with the magnet 86, a central recess or counterbore being provided in its upper surface to accommodate the two rings 33 (not shown) employed to secure it in place. It will be obvious, however, that if a cushioning construction were desired to eliminate noise, the two upper rings 33 might be arranged to overlie the upper face of the disk $2, and thus to engagethe lower face of the magnet 80 upon movement to normal position. A spring 83 generally similar to the springs 62 and 71 is shown as provided to urge the push button toward its normal position, the spring being engaged between the lower surface of the disk 82 and the upper surface of the panel 14. As shown, the lower retainer ring 33 may be utilized to define a seat for the spring. As previously explained, other biasing means might be employed in place of spring 83, or the force of the magnet alone might be relied upon for return of the push button from operating to normal position.

It will be evident that a snap-action push button construction is provided by utilization of magnetic attraction to dispose the pushbutton in a predetermined normal position, since the initially relatively great holding force of the magnet, when once overcome by pressure on the key or push button, becomes progressively less as the push button is moved from the normal position toward its other or operating position. The pressure results in a momentum or impetus upon release or initial separating movement of the magnet and the co-operating body or disk which carries through the movement of the push button to the operating position. Since the magnetic attraction becomes weaker as the movement continues, there is no appreciable resistance to the travel of the push button which thus is moved through its full travel distance, to the limit provided by the stop means. While resilient or other biasing means may be employed. as described hereinabove to urge the push button or key toward normal position, such means need not be very strong, and afford no substantial opposition to the pressure effecting the push button movement. a By comparison, the magneti holding force is so great that the biasing force is prac-' tically negligible as a factor in resisting the movement of the push button to the operating position.

In each of FIGURES 6 and 7, there is shown an annular magnet which may be employed as the magnet 32 or 80. In FIGURE 6, the magnet 85 has diametrically opposed north and south poles 86 and 87 represented in the drawing by the notations N and S, respectively, while in FIGURE 7 the magnet 90 has its north pole 91 along the outer periphery or circumference of the magnet, and the south pole 92 along the inner edge, or about the central opening thereof. The respective poles are represented by series of letters N and S, as shown. Either of these forms of magnet may be employed, the choice depending upon the particular circumstances.

It should be noted that the invention is not limited to the use of permanent magnets, since electromagnetic means may be employed in addition to or substitution for the permanent magnet or magnets as disclosed, in appropriate circumstances.

While, for convenience in description, the terms upper and lower, and the like, have been employed, it is to be understood that the invention and the particular constructions disclosed are not limited to this particular relationship of the parts, and that the push button construction may be disposed in any desired position.

It is also to be understood that the invention is not limited to the particular embodiments thereof specifically disclosed herein, which are illustrative and exemplary, since modifications and variations thereof may be made without departing from the spirit and scope of the inventive concept.

We claim:

1. A snap-action, push button construction comprising a pair of spaced plates and an enclosing cover overlying one of said plates, said plates and cover having aligned openings therethrough, and a plunger longitudinally reciprocal through said aligned openings having one end protruding through the cover opening and its other end extending through the opening in the other one of said spaced plates, said plunger having stop means between said two plates which engage the other plate about the opening therein when the plunger is depressed a determined distance to limit further depression thereof, an annulus of magnetic material secured about said plunger intermediate its said stop means thereon and the first mentioned plate, said annulus having engagement means, a compressible spring encircling said plunger and disposed between said other plate and said engagement means of the annulus so as to be compressed when the plunger is depressed to the limit defined by said stop means, at least the first mentioned plate having a portion of magnetic material located about said plunger, one of said portion and the annulus comprising a magnet attracted to the other when adjacent thereto by a force sufiicient to securely hold the plunger against said portion of the first mentioned plate, the force of said magnetic attraction progressively decreasing as the annulus is moved away from said portion upon depression of the plunger, the compressible spring exerting a minimal force on the plunger which when the stop means engages the other plate is still considerably less than the force of the magnetic attraction which exists between the annulus and portion of the first mentioned plate when adjacent each other, said magnetic attraction thereby constituting an initially strong maximum force to be overcome by exerting an outside force against the one end of the plunger which protrudes through the opening in the cover, and the resistance to which outside force rapidly decreases as the annulus is moved away from the first mentioned plate whereby the moment of the outside force initially developed against the one end of the plunger acts substantially unchecked to cause full depression of the plunger to where the stop means engages the other plate, and said spring acting, upon release of said outside force, to move the plunger back to where the magnetic attraction between the annulus and portion of the first mentioned plate is suflicient to return the plunger to its initial position with its an- 10 nulus against said portion of the first mentioned plate.

2. A push button construction comprising a permanent magnet, magnetically permeable pole pieces extending in spaced relation to each other from opposite poles of said magnet and each having an aperture therein aligned with an aperture in the other, a plunger of magnetically permeable material mounted in said apertures for reciprocation relative to said pole pieces and providing a flux path tllerebetween, a body of magnetic material projecting laterally from said plunger attracted to one of said pole pieces to locate the plunger in a predetermined position, the plunger being movable to another position upon application of force thereto overcoming said attraction, means limiting travel of the plunger, and means biasing the plunger toward said predetermined position.

3. A push button construction comprising a magnet structure, a plunger of magnetically permeable material mounted for reciprocation relative to said magnet structure and providing a flux path between the poles thereof, and a body of magnetic material on said plunger attracted by one of said poles to locate the plunger in a predetermined position, the plunger being movable to another position upon application of force thereto overcoming said attraction.

4. A snap action push button construction comprising a permanent magnet structure including a permanent magnet and a pair of pole pieces extending in spaced relation to each other from the opposite poles of said magnet and each having aperture therein aligned with an aperture in the other, a plunger of magnetically permeable material extending through said apertures in reciprocable relation to said pole pieces and providing a flux path therebetween, a body of magnetic material on said plunger attracted to one of the pole pieces to locate the plunger in a predetermined position, the plunger being movable to another position upon application thereto of force overcoming said attraction, the magnetic atraction affording at least a major part of the resistance to said force, non-magnetic cushioning means between said one pole piece and said body, stop means limiting movement of the plunger under said force to determine said other position, and resilient electrical contact means operable by the plunger and engaging therewith for biasing thereof toward said predetermined position, the spacing of the body from the other pole piece in both said positions being sufficient to prevent any appreciable magnetic attraction therebetween.

5. A push button construction comprising a magnet structure including a pair of spaced polar extensions, a plunger reciprocable transversely of said extensions, a body of magnetic material on said plunger attracted by one of the extensions to locate the plunger in a predetermined position, the plunger being movable toward the other extension to another position upon application thereto of force overcoming said attraction, and means for determining said other position, the spacing between said body and other extension in both said positions being suflicient to preclude substantial magnetic attraction therebetween.

6. A snap action push button construction comprising a permanent magnet structure including a permanent magnet and a pair of spaced pole pieces extending from the opposite poles of said magnet and each having an aperture therein aligned with an aperture in the other, a plunger of magnetically permeable material extending through said apertures in reciprocable relation to said pole pieces and providing a flux path therebetween, a body of magnetic material on the plunger projecting laterally therefrom between and attracted by both pole pieces, and resilient electrical contact means operable by the plunger and engaging therewith for biasing thereof toward one of the pole pieces for attraction thereto and location thereby in a predetermined position, the plunger being movable toward the other pole piece to another 11 position upon application thereto of force overcoming the attraction between said one pole piece and body and also the force of said biasing means, the attraction between said other pole piece and body progressively increasing upon plunger movement toward the other pole piece and counteracting the biasing means to assure full travel of the plunger under said overcoming force, the force of the biasing means being greater than the maximum attraction between the body and other pole piece, and said body defining stop means to limit movement of the plunger in both directions and determine both said positions.

7. A push button construction comprising a magnet structure including a pair of spaced polar pieces, a plunger of magnetically permeable material reciprocable trans versely of said pieces and providing a flux path therebetween, a body of magnetic material on the plunger between and attracted by both pole pieces, and means biasing the plunger toward one of the pole pieces for References Cited in the file of this patent UNITED STATES PATENTS 2,410,746 Raettig Nov. 5, 1946 2,547,171 Prouty Apr. 3, 1951 2,816,254 Canepa Dec. 10, 1957 2,847,528 Combs Aug. 12, 1958 2,896,043

Andrews July 21, 1959 

3. A PUSH BOTTON CONSTRUCTION COMPRISING A MAGNET STRUCTURE, A PLUNGER OF MAGNETICALLY PERMEABLE MATERIAL MOUNTED FOR RECIPROCATION RELATIVE TO SAID MAGNET STRUCTURE AND PROVIDING A FLUX PATH BETWEEN THE POLES THEREOF, AND A BODY OF MAGNETIC MATERIAL ON SAID PLUNGER ATTRACTED BY ONE OF SAID POLES TO LOCATE THE PLUNGER IN A PREDETERMINED POSITION, THE PLUNGER BEING MOVABLE TO ANOTHER POSITION UPON APPLICATION OF FORCE THERETO OVERCOMING SAID ATTRACTION. 